Objectives Cerebrovascular accidents, or strokes, remain a major concern for the modern healthcare system. More than 700,000 strokes occur in the US each year, leaving more than 4.8 million chronic stroke survivors. Currently, 15,000 new cases of stroke are seen in the VHA each year, and the stroke-related financial burden placed on the VHA is over $1 billion per year. This cost is expected to rise as the number of Veterans age into an at-risk cohort; approximately 45% of VHA enrollees are aged over 65 years and 40% are aged between 45 and 65 years. Of deficits commonly resulting from stroke, apraxia is reported to occur in 33% to 75% of left hemisphere stroke patients and is manifest as a disturbance in understanding the appropriate use and advantage of tools to manipulate objects. Conceptual apraxia (CA) is a specific form of apraxia which impairs the ability to solve tool-related or mechanical problems, and results from lesion to commonly affected areas of the brain. The loss of tool-object associative knowledge is a significant impairment resulting from stroke, and may lead to deficits in activities of daily living. Because aging and stroke-injured populations are highly relevant to the VHA, the central purpose of the proposed research is to determine, in Veterans, the impact of brain age and brain health on relational/associative knowledge through a tool-use model. Research Plan: These objectives can be accomplished several ways. First, we will directly compare tool-object associative knowledge in the young versus the healthy older brain to determine age effects. Second, while comparing tool-use knowledge in the healthy older brain versus stroke affected persons with and without apraxia, we can determine brain health effects. Long term objectives will build from this foundation to focus on the potential of cognitive motor rehabilitation training to slow age-related loss of praxis knowledge and improve cognitive motor function in apraxia Methods Electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) will be used to evaluate the neural mechanisms which support the comprehension of tools in the healthy young and older brains and in chronic stroke patients with and without CA. We will focus on 1) context challenges, where participants evaluate contextually correct (e.g. key to open a lock) or incorrect (e.g. key to eat soup) usage of a tool and 2) action-orientation challenges, where participants evaluate tool usage in the correct context but with either a correct (e.g. screwdriver held by handle) or incorrect (e.g. screwdriver held by the bit) action-orientation. Relevance: These studies will identify neural mechanisms for specific aspects of tool comprehension, which are important for our ability to interact with our environment. Our results will better establish which cortical areas are involved in comprehending correct tool-object contextual usage and action-orientation. By extension, this will inform us of the impact of Veteran brain age and brain health on specific types of relational/associative processes, those supporting the use of tools. This work will form the basis of future studies into the effectiveness of rehabilitation therapies on improving cognitive motor function in aging and neurologically impaired Veterans, and will lead to treatments or preventative strategies for Veterans with diminished cognitive motor function.